Vacuum testing apparatus



April 12, 1960 D, SQMERS ETAL 2,932,187

VACUUM TESTING APPARATUS Filed Sept. 27, 1957 A anMA/v Asa/vans flow/1w ABM/var? United States atent ice VACUUM 'msrmo APPARATUS Norman D. Somers and Ronald A. Barnett, Brownsburg,

Quebec, Canada, assignors to Canadian Industries Limied, Montreal, Quebec, Canada, a corporation of v anada Application September 27, 1957, Serial No. 686,786 Claims priority, application Canada October 11, 1956 1 Claim. (CI. 73-40) metal is elongated while maintaining the required diam-' eter. In the course of these operations, where the metal is being cold worked, severe stresses and strains are introduced which may cause rupturing to occur at one or more points in the tube. Such rupturing is most likely to occur in the final drawing operations, 'where the tube wall is very thin, and results in minute cracks or pin holes in the tube.

- Holes in detonator tubes are undesirable because particles of the very sensitive detonating composition may be forced through the holes where it will be exposed and subject to frictional detonation, and also because moisture may enter through the holes and desensitize the detonat-' ing composition. This is particularly likely to occur when the detonator is in place in a wet bore hole and often subject to a high hydrostatic head. Desensitizing of the detonating composition results'in a misfire which in turn results in unexploded explosive being left in the bore holes or thrown out in the muck. The hazard involved in disposing of an unexploded charge either in a bore hole or mixed in with the muck is very great and has been the cause of fatal accidents. 7 a

Great stress is therefore laid on the detecting of all holes in detonator tubes. One widely used method of accomplishing this has been to take a number of tubes and place them over a light box so that light from the box is sealed oif. The tubes are then visually inspected one by one for evidence of light showing through pin holes or cracks in the tube wall. This method eliminates the majority ,of faulty tubes but is not completely effective because it is possible to have cracks that are formed in such away that they constitute a light trap. Furthermore, the method is time consuming and hence ineflicient; It has been recognized that better inspection could be obtained by applying a vacuum to the tube in combination with a means for detecting the breakdown of this vacuum, which will occur if the tube wall is perforated. With a mechanical means for performing the actual inspection, it is also possible to provide automatic feeding and ejecting devices, thus increasing the efiiciency of the operation. V

The vacuum testing machines produced to date are all deficient in two respects: (1) the method of producing and holding the vacuum involves sliding metal members, subject to frictional wear and consequent imperfect functioning of the mechanism; and (2) the mouth of the tube is sealed by pressing it'against a resilient member, such as rubber, which becomes cut from the sharp tube edge with a resultant loss of vacuum and, hence, a resultant imperfect functioning of the mechanism.

It is an object of this invention to overcome the aforesaid disadvantages by providing means for producing vacuum which involve no metal contact surfaces and thus eliminate failure of the mechanism due to frictional wear, and wherein the sealing of the mouth of the tube is such that the resilient member involved is not subject to cutting by the sharp edge of the tube mouth.

Another object of the invention is to provide positive mechanical means for removal of both good and faulty tubes from' the mechanism after testing, thus eliminating the dependence on gravity inherent in other testing mechanisms.

Additional objects of the invention will be apparent hereinafter.

Broadly speaking, the invention is based on the use of a vertically movable mercury cell having an upperand a lower electrical contact, said cell being connected to one end of a passage in a rotating plate, the otherend of said passage being provided with a ring-shaped pocket into which a tube is inserted in air-tight condition. The down Ward movement of the cell produces a vacuum in the pas rent continues to flow since the vacuum in the passage is not broken and the reject mechanism is not actuated.

The apparatus of the invention thus comprises, in combination, a horizontal, circular, rotatable plate member mounted upon a vertical shaft and provided with a plurality of inverted U-shapedhollow passages equidistantly spaced near the periphery of its lower surface, radially thereof; a cylindrical stationary cam mounted upon said vertical axis and having an endless groove extending downwardly and thence upwardly around its periphery; a plurality of vertically movable mercury-filled cupshaped members, equal in number to and of greater diameter than said hollow passages, radially spaced from said cam opposite the inward openings of said hollow passages and attached to said axis for rotation therewith, each of said members having an arm extending radially from i'tsside wall into said endless groove for guiding its vertical movement as it rotates; aplurality of hollow tubes, equal innumber to and of smaller diameter than said cup-shaped members, attached to said plate member around the inward openings of said hollow passages and extending downwardly therefrom into said cup-shaped members; an anodic rod extending downwardly into each hollow tube to a point intermediate thereof; a cathodic rod extending downwardly into each cup-shaped member within the space between the side Wall thereof and the hollow tube; means positioned around the outward opening of each hollow passage adapted to receive and hold the open end of a tube to be tested in air-tight relationship with said opening; means for feeding tubes to be tested into said receiving and holding means when said cup-shaped members are in their upper position; means dependent upon the electrical circuit between said anodic and cathodic rods for ejecting faulty tubes from said receiving and holding means when said cup-shaped members are in their lower position; and means for ejecting good tubes from said receiving and holding means before said cup-shaped members reach their upper position.

Preferably, the tube receiving and holding means comprise an inwardly-flanged ring-shaped pocket attached to the plate member around the outward opening'of the Patented Apr. 12,, 19(50.

. 3 hollow passage and a resilient ring contained within said pocket in abutting relationship with the side thereof and adapted to surround the open end of the tube to be tested in abutting relationship.

The apparatus will be better understood by referenceto the accompanying drawing which illustrates one embodiment thereof in cross-sectional view.

In, the drawing 1 is the horizontal, circular, rotatable plate membermounted upon the vertical shaft 2, to which isattached a plurality of cup-shaped members 3 in such a way that each one revolves integrally with the plate member 1 but is free to move. vertically. The vertical movement of the cup-shaped members 3 is directed by the. arms 4 attached to the side walls thereof; and, which extend into the endless groove 5 of the cylindrical stationary cam 6.

The horizontal, circular, rotatable pl'ate membefl. is

provided with a plurality of inverted U-shaped. hollow passages 7 equidistantly spaced near the periphery ofits lower surface, radially thereof, the. inward opening, of each passage being surrounded by a hollow tube, 8, extending into the mercury 9 of a cup-shaped. member 3.

An anodic rod 10 extends into the hollowv tube8 and. a. cathodic rod 11 extends into the cup-shaped: member 3. between the side wall thereof and the hollow tube 8,.

each rod having wires attached to electrical control devices (notshown in the drawing).

The. outward opening of each hollow passage. 7 is surrounded by an inwardly-flanged ring-shaped pocket 12 which contains a resilient ring 13 in abutting relationship with the side thereof and which receives the tube 14 to be tested.

In operation, the tube 14 to be tested is, fed intothe resilient ring 13 contained within the pocket 12 by known external feeding means (not shown in thedrawing Because of the abutting relationship of the resilient ring with the pocket wall and the tube wall, an air-tight seal is effected. As the plate member ,1 rotates, the cup.-

shaped member 3, which was in an upper position when the tube 14 was inserted into the pocket 12 and ring 13, is caused to move down, thus creating a vacuum inside the hollow passage 7 and the tube 14. With a good tube, the vacuum holds the mercury 9 up inside the hollow tube 8, thus maintaining an electrical circuit between rods 10 and 11. However, if the tube 14 is faulty, the

vacuum is broken, thus partially allowing the mercury- 9 to drop inside the hollow tube 8 and breakingthe electrical circuit between rods 10 and 11.

The breaking of the electrical circuitcauses electro' and the number 14 has been used to designate tubes which are undergoing testing.

From the above description, it will readily be seen that the vacuum testing apparatus of this invention involves no metallic friction whatever arid makes use of tube holding means which are not-subject to cutting by the sharp edge of the tube opening, thus overcoming all the disadvantages of the vacuum testing apparatus of the prior art.

It will also be understood that the aforesaid description and the accompanying drawing illustrate only a preferred embodiment of the apparatus of this invention and that many modifications can be imparted thereto without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Apparatus for vacuum testing metal tubes closed at one end. and comprising, in combination, a horizontal circular rotatable. plate member provided with a plurality of inverted U-shaped hollow passages equidistantly spaced near the periphery of its lower surface radially thereof, each of said passages having an inner opening and an outer opening on said lower surface; a vertical shaft on which said plate member is mounted; means for producing the said vacuum comprising a cylindrical stationary; cam mounted upon said vertical shaft and having an endless groove extending downwardly and thence upwardly around its periphery; a plurality of vertically movable, mercury-filled cup-shaped members, equal in number to and of greater diameter than said hollow passages, radiaally spaced from said cam opposite the inner openings of said hollow passages and attached to said shaft for rotation therewith, each of said members having an arm extending radially from its side wall into said endless groove for guiding its vertical movement as it rotates; a plurality of hollow tubes, equal in number to and of smaller diameter than said cup-shaped members, attached to said plate member around the inner openings of said hollow passages and extending downwardly therefrom into said cup-shaped members; an anodic rod extending. downwardly into each hollow tube to a point intermediate. thereof and a cathodic rod extending downwardly into each cup-shaped member within the space between the side wall thereof and the hollow tube; and means for receiving and holding the open ends of tubes to be tested.

References Cited'in the file of this patent" UNITED STATES PATENTS 2,309,231 Bagley Jan. 26', 1943, 2,433,043 Gray Dec. 23, 1947 2,548,645 Ashcroft et al Apr. 10, 1951 

